1. Field of the Invention
The present invention relates to a lubrication structure of an engine, and more particularly to a fuel pump lubrication device that is capable of effectively lubricating a tappet of the engine, a tappet roller, and a cam.
2. Description of Related Art
Technologies for a gasoline direct injection (GDI) engine have been studied in order to improve fuel consumption and performance of the engine.
The GDI engine technologies are methods in which only air is drawn into the combustion chamber and is compressed and then fuel is injected therein, while in the case of a conventional gasoline engine, power is generated in a period of an intake stroke, a compression stroke, an ignition stroke, and an exhaust stroke process of an air/fuel mixture. Such a method is similar to a compressed ignition engine method.
Due to a high compression ratio of the GDI engine, a high compression ratio that is capable of exceeding a limit of a usual gasoline engine results in maximization of fuel consumption.
The GDI engine depends on a high fuel pressure, and a high performance fuel pump is required.
The fuel pump is mechanically driven by a cam so as to operate a tappet, and friction inside the fuel pump is generated. A great deal of friction occurs in the fuel pump due to the high pressure of the fuel.
Therefore, a lubrication device of the fuel pump for compressing the fuel in the GDI engine has been studied in order to improve durability and performance of the GDI engine.
To solve the problems, as an example, a method of lubricating the cam with oil stored in a predetermined space when a camshaft for the fuel pump is rotated. Such a method has a merit of simplifying the structure, but it is difficult to lubricate throughout the fuel pump, and further it is difficult to lubricate it of slanted surface.
Further, there is a method, as another example, which forms an oil hole at the cam so as to flow oil therein.
However, the method mentioned above has a drawback in that it is capable of lubricating only a specific part that is provided with an oil hole, and it is impossible to form a hole at a portion of the cam contacting the tappet of the fuel pump.
In addition, the cam rotates in such a state in which it rotatably contacts the roller mounted at the bottom of the cam so as to operate the tappet upwardly and downwardly, and the conventional tappet lubrication structure of the engine guides the tappet upwardly and downwardly by the roller between the tappet and the cam, but contact surfaces between the tappet and the fuel pump adaptor and between the cam and the roller are not lubricated smoothly thereby inducing abrasion, and consequently durability and rotation thereof are deteriorated.
Therefore, due to the abrasion occurring at the roller interposed between the cam and the roller tappet, durability thereof is deteriorated and thereby manufacturing cost is increased, and noise occurs at the connected portion thereof.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.